Lubricating oil composition for improved oxidation, viscosity increase, oil consumption, and piston deposit control

ABSTRACT

An engine oil lubricant composition having improved control of oxidation viscosity, and piston deposits is provided. The composition further exhibits performance on the ASTM Sequence IIIG Test of about 90% or less kinematic viscosity increase at 40° C. and about 5.5 or more merits average weighted piston deposits. The composition meets or exceeds the standards of both the ILSAC GF-4 and the General Motors GM4718M specifications.

TECHNICAL FIELD

The present disclosure is related to an engine oil lubrication composition, and specifically to an engine oil lubrication composition having improved control of oxidation, viscosity increase, piston deposits, and oil consumption.

BACKGROUND

Lubricating oils that are suitable for use in modern engines must meet industry specified performance benchmarks, meeting or exceeding published standards such as the International Lubricant Standardization and Approval Committee (“ILSAC”) GF-4 standard and the American Petroleum Institute's SM standard. One of the performance tests that must be passed to meet ILSAC GG-4 is the ASTM Sequence IIIG Test, which evaluates the ability of a lubricating oil composition to regulate oil thickening and piston cleanliness.

The ASTM Sequence IIIG test is designed around a General Motors 3800 Series II 3.8L V-6 engine run at 125 horsepower, 3600 RPM, and 150° C. oil temperature for 100 continuous hours. The IIIG allows test oils to be evaluated for performance under particularly harsh conditions in order to better assess the real-world performance capabilities of the oils.

In order to meet the minimum standard for GF-4 or SM, a test oil composition must have an ASTM Sequence IIIG viscosity increase of 150% or less, and weighted piston deposits (“WPD”) of 3.5 or greater. The Sequence IIIG test performance requirements are about 50% more stringent than the previous ASTM Sequence IIIF test. However, certain Original Equipment Manufacturers (“OEMs”) have demanded even higher performance levels for their specific families of engines. For example, the General Motors GM4718M specification requires an ASTM Sequence IIIG viscosity increase of 90% or less and WPD of 5.5 or greater.

It is therefore an object of the current disclosure to provide an engine oil composition capable of meeting or exceeding the standards imposed by the GM4718M specification, as well as providing an engine oil composition that meets or exceeds the standards of GF-4 and SM with regard to control of oxidation, viscosity, piston depositions, and oil consumption.

SUMMARY

With regard to the above and other objects, an embodiment of the present disclosure provides an engine oil lubricant composition capable of achieving an ASTM Sequence IIIG test kinematic viscosity increase of about 90% or less at 40° C. and average weighted piston deposits having about 5.5 or more merits. The composition may comprise a major amount of a synergistic base oil mixture consisting essentially of a Group III base oil, a Group IV base oil, and a Group V base oil.

In another embodiment, a method for providing an engine oil lubricant composition capable of achieving an ASTM Sequence IIIG test kinematic viscosity increase of about 90% or less at 40° C. and average weighted piston deposits having about 5.5 or more merits may comprise combining a Group III base oil, a Group IV base oil, and a Group V vase oil into a synergistic base oil mixture.

In another embodiment, a method for lubricating an engine component may comprise contacting the engine component with a lubricant composition having an ASTM Sequence IIIG test kinematic viscosity increase of about 90% or less at 40° C. and average weighted piston deposits having about 5.5 or more merits. The lubricant composition may comprise a major amount of a synergistic base oil mixture of a Group III base oil, a Group IV base oil, and a Group V base oil.

Lubricant compositions of the present disclosure may employ a synergistic mixture of base oil stocks to provide a substantial performance improvement when compared to conventional lubricant compositions. Some advantages of the presently disclosed embodiments are a substantial and unexpected improvement in kinematic viscosity increase, a substantial and unexpected improvement in oil consumption, and a substantial and unexpected improvement in average weighted piston deposits, as compared to conventional lubricating oil compositions that are comprised of either a Group II base oil that is free of a mixture of a Group III base oil, a Group IV base oil, and a Group V base oil; or a Group III base oil that is free of a mixture of a Group IV base oil and a Group V base oil.

Additional objects and advantages of the disclosure will be set forth in part in the description which follows, and/or can be learned by practice of the disclosure. The objects and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.

DESCRIPTION

As used herein, “hydrocarbon” means any of a vast number of compounds containing carbon, hydrogen, and/or oxygen in various combinations. The term “hydrocarbyl” refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

(i) hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliplhatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form an alicyclic radical);

(ii) substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of the description herein, do not alter the predominantly hydrocarbon substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);

(iii) hetero-substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this description, contain atoms other than carbon in a ring or chain otherwise composed of carbon atoms. Hetero-atoms include sulfur, oxygen, nitrogen, and encompass substituents such as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

The present disclosure is directed toward an engine oil lubricant composition. An engine oil lubrication composition may comprise a major amount of a base oil mixture comprising at least one Group III base oil, at least one Group IV base oil, and at least one Group V base oil. Such a synergistic base oil mixture has been shown to provide a substantial performance improvement in the ASTM Sequence IIIG test over conventional lubrication compositions comprised substantially of either Group II or Group III base oils.

The lubricant compositions may comprise a major amount of a mixture of one or more base oil stocks plus a minor amount of a lubricant additive composition. The base oil may comprise one ore more base oil stocks in which the additive composition is soluble the various components are selected according to the specifications of the engine manufacturer to meet certain requirements for test parameters such as viscosity and the amount of piston deposit formation, among others. Tests, such as the ASTM Sequence IIIG, are performed on potential oil compositions in order to ensure that the standards of the engine manufacturer are met.

As used herein, the terms “oil composition,” “lubrication composition,” “lubricating oil composition,” “lubricating oil,” “engine oil,” “lubricant composition,”“fully formulated lubricant composition,” and “lubricant” are considered synonymous, fully interchangeable terminology referring to the finished lubrication product comprising a major amount of a base oil plus a minor amount of an additive composition.

As used herein, the terms “additive package,” “additive concentrate,” and “additive composition” are considered synonymous, fully interchangeable terminology referring the portion of the lubricating composition excluding the major amount of base oil stock mixture.

Base Oil

An engine oil lubricant composition according to the present disclosure may comprise a major amount of a synergistic mixture of at least one Group III base oil, at least one Group IV base oil, and at least one Group V base oil. A major amount is defined to be greater than 50 wt % of the total lubricant composition, such as greater than or equal to 80 wt % of the total lubricant composition. The balance of the lubricant composition may be provided by a minor amount of an additive composition. A minor amount is defined to be less than 50 wt % of the total lubricant composition and, as a further example, less than or equal to 20 wt % of the total lubricant composition.

The base oil mixture may comprise a mixture of one or more of each of Group III, Group IV, and Group V base oils. At least one base oil from each of Groups III, IV, and V must be included in the base oil mixture in order for the lubricating composition to benefit from a synergy among the base oils. Suitable portions of each class of base oil may include up to about 50 wt % of a Group III base oil, and from about 20 wt % of a Group IV base oil, and from about 5 wt % to about 25 wt % of a Group V base oil, based on the total weight of the base oil mixture. Suitable portions of each class of base oil stock may include, as another example, from about 30 wt % to about 50 wt % of a Group III base oil, and from about 20 wt % to about 35 wt % of a Group IV base oil, and from about 5 wt % to about 25 wt % of a Group V base oil, based on the total weight of the base oil mixture.

The Group III base oils suitable for use in formulating engine oil lubricant compositions may be selected from any of the natural oils or mixtures thereof. Natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil) as well as mineral lubricating oils such as liquid petroleum oils and solvent treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-napthenic types. Oils derived from coal or shale are also suitable. The base oil typically has a viscosity of about 2 to about 15 cSt or, as a further example, about 2 to about 10 cST at 100° C. Further, embodiments may contain a mixture of more than one Group III base oil having the same or different viscosity.

The Group IV or V base oils may include alkyl esters of dicarboxylic acids, polyglycols and alchols, polyaphaolefins, including polybutenes, alkylbenzenes, organic esters of phosphoric acids, and polysilicone oils. Synthetic oils include hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene isobutylene copolymers, etc.); poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc. and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, di-nonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls, terphenyl, alkylated polyphenyls, etc.); alkylated diphenyl ethers and alkylated dipheny sulfides and the derivatives, analogs and homologs thereof and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc., constitute another class of known synthetic oils that may be used. Such oils are exemplified by the oils prepared through polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having an average molecular weight of about 1000, diphenyl ether of polyethylene glycol having a molecular weight of about 500-1000, diphenyl ether of polyethylene glycol having a weight of about 1000-1500, etc.) or mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C₃₋₈ fatty acid esters, or the C₁₃ Oxo acid diester of tetraethylene glycol.

Another class of synthetic oils that may be used includes the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol, etc.) Specific examples of these esters include dibutyl adipate, di(2-ethylehexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include those made from C₅ to C₁₂ monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylol propane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc. Further, an oil derived from a gas-to-liquid process may also be suitable.

Group V base oils may comprise non-PAO synthetics, including, but not limited to, synthetic esters, diesters, polyolesters, alkylated naphthalenes, alkylated benzenes, and the like. A suitable Group V base oil is a trimethylolpropane tri-C8/C10 ester having a viscosity of 4.4 cSt at 100° C. and a viscosity index of 140.

Hence, the base oil used which may be used to make the engine oil lubrication compositions as described herein may be selected from any of the base oils in Groups III-V as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. Such base oil groups are as follows:

TABLE 1 Base Oil Group¹ Sulfur (wt %) Saturates (wt %) Viscosity Index Group I >0.03 and/or <90 80 to 120 Group II ≦0.03 and ≧90 80 to 120 Group III ≦0.03 and ≧90 ≧120 Group IV all polyalphaolefins (PAOs) Group V all others not included in Groups I–IV ¹Groups I–III are mineral oil base stocks.

As set forth above, the base oil may include a polyalphaolefin (PAO). Typically, the poly-alpha-olefins are derived from monomers having from about 4 to about 30, or from about 4 to about 20, or from about 6 to about 16 carbon atoms. Examples of useful PAOs include those derived from octene, decene, mixtures thereof, and the like. PAOs may have a viscosity of from about 2 to about 15, or from about 3 to about 12, or from about 4 to about 8 cSt at 100° C. Examples of PAOs include 4 cSt at 100° C. poly-alpha-olefins, 6 cST at 100° C. poly-alpha-olefins, and mixtures thereof. Mixtures of mineral oil with the foregoing poly-alpha-olefins may be used.

The base oil may include an oil derived from Fisher-Tropsch synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons are made from synthesis gas containing H₂ and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing in order to be useful as the base oil. For example, the hydrocarbons may be hydroisomerized using processes disclosed in U.S. Pat. Nos. 6,103,099 or 6,180,575; hydrocracked and hydroisomerized using processes disclosed in U.S. Pat. Nos. 4,943,672 or 6,096,940; dewaxed using processes disclosed in U.S. Pat. No. 5,882,505; or hydroisomerized and dewaxed using processes disclosed in U.S. Pat. Nos. 6,013,171; 6,080,301; or 6,165,949.

Unrefined, refined and refined oils, either natural or synthetic (as well as mixtures of two or more of any of these) of the type disclosed hereinabove can be used in the base oils. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. For example, a shale oil obtained directly from retorting operations, a petroleum oil obtained directly from primary distillation or ester oil obtained directly from an esterification process and used without further treatment would be an unrefined oil. Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Many such purification techniques are known to those skilled in the art such as solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Rerefined oils are obtained by processes similar to those used to obtain refined oils applied to refined oils which have been already used in service. Such rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques directed to removal of spent additives, contaminants, and oil breakdown products.

Additive Composition

The lubricant composition may include hydrocarbon-soluble additive components selected from, but not limited to, dispersants, friction modifiers, antiwear agents, antioxidants, antifoam agents, detergents, viscosity index improvers, pour point depressants, diluent and the like. Such additive components are typically used in conventional amounts to provide a fully formulated lubricant composition. For the purpose of this disclosure, the foregoing terms relate to primary characteristics of the additive components. It will be appreciated that many of the components may perform multiple functions in the lubricant composition. Accordingly, classification of the additive components is merely for convenience and is not intended to limit the scope of the claimed embodiments.

Dispersants

Dispersants which may be used include, but are not limited to, amine, alcohol, amide, or ester polar moieties attached to the polymer backbone often via a bridging group. Dispersants may be selected from Mannich dispersants as described, for example, in U.S. Pat. Nos. 3,697,574 and 3,736,357; ashless succinimide dispersants as described in U.S. Pat. Nos. 4,234,435 and 4,636,322; amine dispersants as described in U.S. Pat. Nos. 3,219,666, 3,565,804, and 5,633,326; Koch dispersants as described in U.S. Pat. Nos. 5,936,041, 5,643,859, and 5,627,259, and polyalkylene succinimide dispersants as described in U.S. Pat. Nos. 5,851,965; 5,853,434; and 5,792,729.

As used herein the term “succinimide” is meant to encompass the completed reaction product from a reaction between a hydrocarbyl substituted succinic acylating agent and a polyamine and is intended to encompass compounds wherein the product may have amide, amidine, and/or salt linkages in addition to the amide linkage of the type that results from the reaction of a primary amino group and an anhydride moiety.

Of the succinimides, succinimides derived from an aliphatic hydrocarbyl substituted succinic acylating agent in which the hydrocarbyl substituent contains an average of at least 40 carbon atoms are particularly suitable dispersants. Particularly suitable for use as the acylating agent is (a) at least one polyisobutenyl substituted succinic acid or (b) at least one polyisobutenyl substituted succinic anhydride or (c) a combination of at least one polyisobutenyl substituted succinic acid and at least one polyisobutenyl substituted succinic anhydride in which the polyisobutenyl substituent in (a), (b) or (c) is derived from polyisobutenyl or a highly reactive polyisobutenyl having a number average molecular weight in the range of 400 to 5,000.

For the purposes of this disclosure, the term “highly reactive” means that a number of residual vinylidene double bonds in the compound is greater than about 45%. For example, the number of residual vinylidene double bonds may range from about 50% to about 85% in the compound. The percentage of residual vinylidene double bonds in the compound may be determined by well-known methods, such as for example Infra-Red Spectroscopy or C₁₃ Nuclear Magnetic Resonance or a combination thereof. A process for producing such compounds is described, for example, in U.S. Pat. No. 4,152,499.

Another suitable dispersant is a polyalkylene succinimide dispersant derived from the polyisobutenyl (PIB) compound described above wherein the dispersant has a reactive PIB content of at least about 45%. The dispersant may be a mixture of dispersants having number average molecular weights ranging from about 800 to about 3000 and reactive PIB contents of from about 50% to about 60%. The total amount of dispersant in the lubricant composition may range from about 1 to about 10 percent by weight of the total weight of the lubricant composition, and more preferably in the range from about 1 to about 4 percent by weight.

In embodiments of the present disclosure, the dispersant may be a boronated dispersant. In some embodiments, the dispersant may be substantially free of phosphorus. In other embodiments, the dispersant may contain phosphorus. Accordingly, the mixture of dispersant may include a boronated dispersant and a non-boronated dispersant. Either one or both of the boronated and non-boronated dispersants may be made with a highly reactive polyalkylene compound as set forth above. Boronated dispersants may be made by reacting a boron compound or mixture of boron compounds capable of introducing boron-containing species into the dispersants before, during or subsequent to a reaction forming the dispersants. Any boron compound, organic or inorganic, capable of undergoing such reaction may be used. Accordingly, use may be made of such inorganic boron compounds as the boron acids, and the boron oxides, including their hydrates. Typical organic boron compounds include esters of boron acids, such as the orthoborate esters, metaborate esters, biborate esters, pyroboric acid esters, and the like.

Friction Modifiers

One or more oil soluble friction modifiers may be incorporated into the lubricating oil compositions described herein. The friction modifiers may be selected from nitrogen-containing, nitrogen-free, amine-containing, and/or amine free friction modifiers. The friction modifiers may be used in an amount ranging from about 0.02 wt % to 2.0 wt % of the lubricating oil composition. In another example, from 0.05 to 1.0, or from 0.1 to 0.5, wt % of the friction modifiers may be used.

Examples of nitrogen-containing friction modifiers that may be used include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, amino guanadine, alkanolamides, and the like.

Such friction modifiers may contain hydrocarbyl groups that may be selected from straight chain branched chain or aromatic hydrocarbyl groups or admixtures thereof, and may be saturated or unsaturated. Hydrocarbyl groups are predominantly composed of carbon and hydrogen but may contain one or more hetero atoms such as sulfur or oxygen. The hydrocarbyl groups range from 12 to 25 carbon atoms and may be saturated or unsaturated. More suitable are those with linear hydrocarbyl groups.

Other exemplary friction modifiers include alkoxylated amines and alkoxylated ether amines, with alkoxylated amines containing about two moles of alkylene oxide per mole of nitrogen being the most suitable. Such compounds can have hydrocarbyl groups that are linear, either saturated, unsaturated or a mixture thereof. They contain no more than about 12 to about 25 carbon atoms and may contain one or more hetero atoms in the hydrocarbyl chain. Ethoxylated amines and ethoxylated ether amines are particularly suitable nitrogen-containing friction modifiers. The amines and amides may be used as such or in the form of an adduct or reaction product with a boron compound such as a boric oxide, boron halide, metaborate, boric acid or a mono-, di- or tri-alkyl borate.

Sulfides of oils, fats, or polyolefins may also be used as ashless organic friction modifiers. Specifically, for example, mention may be made of sulfurized sperm oil, sulfurized pinene oil, sulfurized soybean oil, sulfurized polyolefin, diakyl disulfide, dialkyl polysulfide, dibenzyl disulfide, di-tertiary butyl disulfide, polyolefin polysulfide, thiadiazole type compound such as bis-alkyl polysulfanyl thiadiazole, and sulfurized phenol. Among these compounds, dialkyl polysulfide, dibenzyl disulfide, and thiadiazole type compound are desirable. Particularly desirable is bis-alkyl polysulfanyl thiadiazole.

Organic, ashless (metal-free), nitrogen-free friction modifiers which may be used in the lubricating compositions disclosed herein are known generally and include esters formed by reacting carboxylic acids and anhydrides with alkanols or glycols, with fatty acids being particularly suitable carboxylic acids. Other useful friction modifiers generally include a polar terminal group (e.g. carboxyl or hydroxyl) covalently bonded to an oleophilic hydrocarbon chain. Esters of carboxylic acids and anhydrides with alkanols are described in U.S. Pat. No. 4,702,850.

Another suitable friction modifier to use in embodiments of the present disclosure is an ester such as glycerol monooleate (GMO), in an amount ranging from about 0.1 wt % to about 0.4 wt %, based on the total weight of the lubricating composition. Suitable friction modifiers may include friction modifiers that are substantially free of transition metals, including, but not limited to, titanium and molybdenum.

Antiwear Agents

Metal dihydrocarbyl dithiophosphate antiwear agents that may be added to the lubricating composition of the present invention comprise dihydrocarbyl dithiophosphate metal salts wherein the metal may be an alkali or alkaline earth metal, or aluminum, lead, tin. manganese, nickel, copper, or zinc.

A suitable antiwear agent comprises zinc dihydrocarbyl dithiophosphates (ZDDP), such as oil soluble salts of dihydrocarbyl dithiophosphoric acids which may be represented by the following formula:

wherein R⁷ and R⁸ may be the same or different hydrocarbyl radicals containing from 1 to 18, typically 2 to 12, carbon atoms and including radicals such as alkyl, alkenyl, aryl, arylalkyl, alkaryl and cycloaliphatic radicals. Particularly desired as R⁷ and R⁸ groups are alkyl groups of 2 to 8 carbon atoms. Thus, the radicals may, for example, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, butenyl. In order to obtain oil solubility, the total number of carbon atoms (i.e. R⁷ and R⁸) in the dithiophosphoric acid will generally be about 5 or greater. The zinc dihydrocarbyl dithiophosphate can therefore comprise primary, secondary, or a mix thereof of zinc dialkyl dithiophosphates.

In order to limit the amount of phosphorus introduced into the lubricating composition by ZDDP to no more than 0.1 wt % (1000 ppm) of phosphorus, or as a further example, no more than about 0.12 wt % (1200 ppm) of phosphorus, the ZDDP should desirably be added to the lubricating oil compositions in amounts no greater than from about 0.9 wt % to about 1.3 wt %, based upon the total weight of the lubricating composition. Use of ZDDP in the aforementioned amount may result in the classification of the lubricating oil as a “low phosphorus” lubricating oil. As referenced herein, the term “low phosphorus” may describe an embodiment wherein the lubricating oil composition comprises at least about 250 ppm phosphorus, or as a further example, from about 250 ppm to about 1200 ppm phosphorus.

Antioxidants

Oxidation inhibitors or antioxidants may be included to reduce the tendency of base stocks to deteriorate in service which deterioration can be evidenced by the products of oxidation such as sludge and varnish-like deposits on the metal surfaces and by viscosity growth. Such oxidation inhibitors include hindered phenols, alkaline earth metal salts of alkylphenolthioesters having C₅ to C₁₂ alkyl side chains, calcium nonylphenol sulfide, ashless oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons, sulfurized olefins, diarlyamines, phenolic ester antioxidants, phosphorus esters, metal thiocarbamates and oil soluble copper compounds as described in U.S. Pat. No. 4,867,890. Antioxidants may be added to lubricating oil compositions in amounts ranging from about 1.0 wt % to about 3.0 wt %, based on the total weight of the lubricating oil composition.

Antifoam Agents

Foam control can be provided by many compounds including an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxane. Antifoam agents may be added to lubricating oil compositions in amounts ranging from about 0.001 wt % to about 0.700 wt %, based on the total weight of the lubricating oil composition.

Detergents

Metal-containing or ash-forming detergents may function both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with a long hydrophobic tail, with the polar head comprising a metal salt of an acid organic compound. The salts may contain a substantially stoichiometric amount of the metal in which they are usually described as normal or neutral salts, and would typically have a total base number (“TBN”), as may be measured by ASTM D-2896 of from 0 to 80. It is possible to include large amounts of a metal base by reacting an excess of a metal compound such as an oxide or hydroxide with an acid gas such as carbon dioxide. The resulting overbased detergent comprises neutralized detergent as the outer layer of a metal base (e.g., carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically from 250 to 450 or more.

Known detergents include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, salicylates, and naphthenates and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals, e.g., sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, which may both be present in detergents used in a lubricant, and mixtures of calcium and/or magnesium with sodium. Particularly convenient metal detergents are neutral and overbased calcium sulfonates having TBN of from about 20 to about 450 TBN, and neutral and overbased calcium phenates and sulfurized phenates having TBN of from about 50 to about 450.

In the disclosed embodiments, one or more calcium-based detergents may be used in an amount ranging from about 1.0 wt % to about 5.0 wt %, based on the total weight of the lubricating oil composition. The metal-based detergent may be overbased and the total base number of the overbased detergent may range from about 150 to about 450. The metal-based detergent may comprise an overbased calcium sulfonate detergent or an overbased magnesium sulfonate detergent. The detergent may also be a low base calcium sulfonate detergent, having a base number below about 80.

The detergent may be present in an amount to contribute a metal content of from about 0.01 wt % to about 1.0 wt %. In another embodiment, the detergent may be present in an amount to contribute a metal content of from about 0.01 wt % to about 0.5 wt %. In a further embodiment, the detergent may be present in an amount to contribute a metal content of from about 0.01 wt % to about 0.2 wt %.

Viscosity Index Improvers/Pour Point Depressants

Viscosity Index (“VI”) improvers and pour point depressants include various hydrocarbon-soluble polymers and co-polymers, covering a wide range of possible molecular weights. VI improvers and pour point depressants help maintain the fluidity of the lubricating composition over a wide range of temperatures. Suitable VI improvers and pour point depressants may include derivatives of polystyrene-maleic anhydride copolymers or non-dispersant olefin copolymers, such as ethylene-propylene.

Other Additives

Other conventional additives may also be included in fully formulated lubricant compositions according to the disclosure. Some of the above-mentioned additives may provide a multiplicity of effects; thus for example, a single additive may act as a dispersant-oxidation inhibitor.

The individual additives may be incorporated into a base oil mixture in any convenient way. Thus, each of the components can be added directly to the base oil mixture by dispersing or dissolving it in the base oil mixture at the desired level of concentration. Such blending may occur at ambient temperature or at an elevated temperature.

In another embodiment, all the additives may be blended into a concentrate as described herein as an additive package that is subsequently blended into the base oil mixture to make the finished lubricant. The concentrate may be formulated to contain the additive(s) in amounts suitable to provide the desired concentration in the final formulation when the concentrate is combined with a predetermined amount of a base lubricant.

The fully formulated lubricant composition may employ from about 2 to about 20 wt %, and as another example from about 4 to about 18 wt %, and as a further example from about 5 to about 17 wt % of the concentrate or additive package with the balance comprising a synergistic base oil mixture of a Group III base oil, a Group IV base oil, and a Group V base oil. A base oil composition prepared in accordance with the present disclosure is suitable for mixture with an additive package that contains at least about 250 ppm phosphorus and/or is substantially free of a transition metal other than zinc, including, but not limited to, titanium and/or molybdenum, and yet such a lubricating composition may meet or exceed the performance rating of a lubrication composition having an additive package including a transition metal, including, but not limited to, titanium, and/or molybdenum.

In some embodiments, a lubricant composition may comprise at least about 0.025 wt % (or about 250 ppm) phosphorus, or as a further example, at least about 0.02 wt % (or about 200 ppm) phosphorus. In some embodiments, a lubricant composition may comprise less than about 0.03 wt % (or about 300 ppm) zinc, or as a further example, less than about 0.02 wt % (or about 200 ppm) zinc. In some embodiments, a lubricant composition may be substantially free of a transition metal, such as, but not limited to, molybdenum or titanium. In other embodiments, a lubricant composition may comprise less than about 50 ppm transition metal, or as a further example, less than 40 ppm transition metal.

The following non-limiting example is used to illustrate an embodiment of the present disclosure:

EXAMPLE 1

Table 2 provides a formulation comparison of three SAE 5W-30 test oils: oil A, oil B, and oil C. Oil A is an example of an embodiment of the present disclosure, while oil B is a conventional oil comprised of a base oil having a mixture of Group III base oil stocks, and oil C is a conventional oil comprised of a base oil having a Group II base oil stock. Oils A, B, and C contain identical additive packages, with the exception of oil A requiring less Viscosity Index Improver (“VII”) than oils B and C. Oil A includes a Group V base oil stock that may impart good viscosity to the mixture, so it does not require as much VII to perform comparably to oils having more of the additive, but lacking a Group V base oil stock.

TABLE 2 A B C Wt. % Wt. % Wt. % Test Oil Succinimide Dispersant 1 1.90 1.90 1.90 Succinimide Dispersant 2 1.70 1.70 1.70 Calcium Sulfonate Detergent, at an amount 0.17 0.17 0.17 contributing to a specified calcium level Low Base Calcium Sulfonate Detergent, at 0.07 0.07 0.07 an amount contributing to a specified calcium level ZDDP, at an amount contributing to a 0.078 0.078 0.078 specified phosphorus level Antioxidant 1 0.50 0.50 0.50 Antioxidant 2 0.90 0.90 0.90 Antioxidant 3 0.50 0.50 0.50 Si Antifoam 0.006 0.006 0.006 Mineral Process Oil 0.544 0.544 0.544 Ester-containing Friction Modifier 0.30 0.30 0.30 Non-dispersant Viscosity Index Improver 7.80 9.00 9.20 Pour-point Depressant 0.10 0.10 0.10 Base Oil Group II Mineral Oil, 4.8 cSt @ 100° C. 79.20 Group III Mineral Oil, 4 cSt @ 100° C. 66.40 Group III Mineral Oil, 8 cSt @ 100° C. 37.60 13.00 Group IV PAO, 4 cSt @ 100° C. 28.00 Group V Polyolester, 4.4 cSt @ 100° C. 15.00 Total % 100.00 100.00 100.00

The ASTM Sequence IIIG test for ILSAC GF-4 certification of an engine oil measures such factors as average cam and lifter wear, viscosity increase, oil consumption, and high-temperature piston deposit formation. The test oil is circulated within a GM 3800 series II 3.8L V-6 engine run at 125 horsepower, 3600 RPM, and 150° C. oil temperature for 100 continuous hours.

Oxidation of the engine oil during the ASTM Sequence IIIG test may lead to viscosity increase, increased wear of cams and lifters, and increased piston deposit formation. A test oils composition having improved control of oxidation may also exhibit reduced viscosity increase, reduced wear of cams and lifters, and reduced piston deposit formation on the ASTM Sequence IIIG test, as compared to ASTM Sequence IIIG test results from a test oil composition lacking improved control of oxidation.

TABLE 3 Sequence IIIG Results A B C 100 Hr Vis Increase (150% max) 17% 112% 111% Weighted Piston Deposit (3.5 min) 6.7 4.0 3.8 Avg Cam & Lifter Wear (60 μm max) 19 28 27 Oil Consumption (L) 1.84 3.51 3.84

ASTM Sequence IIIG test results are given for each of the test oil compositions A, B, and C in Table 3. The additive package was held substantially constant for the test oils in order to accurately evaluate and reliably compare the performance of each base oil mixture under the ASTM Sequence IIIG test conditions.

A substantial and unexpected improvement in kinematic viscosity increase, a substantial and unexpected improvement in average weighted piston deposits, and a substantial and unexpected improvement in oil consumption was observed in the ASTM Sequence IIIG test using test oil A comprised of a synergistic mixture of Groups III, IV, and V base oil stocks, as compared to the observed results using test oil B comprised of a Group III base oil stock that is free of a mixture of a Group IV base oil stock and a Group V base oil stock, or the observed results using test oil C comprised of a Group II base oil stock that is free of a mixture of a group III base oil stock, a Group IV vase oil stock, and a Group V base oil stock.

A lubricating composition comprising a base oil composition having a novel synergistic mixture of Groups III, IV, and V base oil stocks, as evidenced by the data put forth herein, provides superior performance on the ASTM Sequence IIIG Test, meeting or exceeding the requirements for both the ILSAC GF-4 and the more stringent General Motors GM4718M specifications. The presently disclosed lubricating composition provides an unexpected and substantial improvement in ASTM Sequence IIIG test performance when compared to the Sequence IIIG test performance of conventional lubricating compositions.

At numerous places throughout this specification, reference has bene made to a number of U.S. patents and publications. All such cited documents are expressly incorporated by reference into this disclosure as if fully set forth herein.

Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. As used throughout the specification and claims, “a” and/or “an” may refer to one or more than one. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, percent, ratio, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the board scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurmeents. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

The foregoing embodiments are susceptible to considerable variation in practice. Accordingly, the embodiments are not intended to be limited to the specific exemplifications set forth hereinabove. Rather, the foregoing embodiments are within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.

The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part hereof under the doctrine of equivalents. 

1. An engine oil lubricant composition capable of providing improved viscosity increase control and piston cleanliness, wherein the lubricant composition comprises: a major amount of a synergistic base oil mixture consisting essentially of at least one Group III base oil, at least one Group IV base oil, and at least one Group V base oil.
 2. The lubricant composition of claim 1, wherein the Group III base oil is present in an amount of up to about 50 wt %, the Group IV base oil is present in an amount from about 20 wt % to about 45 wt %, and the Group V base oil is present in an amount from about 5 wt % to about 25 wt % based on the base oil mixture.
 3. The lubricant composition claim 1, further comprising a minor amount of an engine oil additive composition.
 4. The lubricant composition of claim 1, wherein the composition comprises at least about 250 ppm phosphorus.
 5. The lubricant composition of claim 1, wherein the composition is substantially free of a transition metal other than zinc.
 6. The lubricant composition of claim 5, wherein the transition metal is selected from the group consisting of titanium and molybdenum.
 7. The lubricant composition of claim 1, wherein the composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 8. The lubricant composition of claim 1, wherein the composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 9. The lubricant composition of claim 1, wherein the composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 10. The lubricant composition of claim 1, wherein the composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 11. A method for providing an engine oil lubricant composition capable of achieving an ASTM Sequence IIIG Test kinematic viscosity increase of about 90% or less at 40° C. and average weighted piston deposits having about 5.5 or more merits, comprising combining a Group III base oil, a Group IV base oil, and a Group V base oil into a synergistic base oil mixture.
 12. The method of claim 11, wherein the Group III base oil is present in an amount of up to about 50 wt %, the Group IV base oil is present in an amount from about 20 wt % to about 45 wt %, and the Group V base oil is present in an amount from about 5 wt % to about 25 wt % based on the base oil mixture.
 13. The method of claim 11, wherein the lubricant composition comprises at least about 250 ppm phosphorus.
 14. The method of claim 11, wherein the lubricant composition is substantially free of a transition metal other than zinc.
 15. The method of claim 14, wherein the transition metal is selected from the group consisting of titanium and molybdenum.
 16. The method of claim 11, wherein the lubricant composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 17. The method of claim 11, wherein the lubricant composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 18. The method of claim 11, wherein the lubricant composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 19. The method of claim 11, wherein the lubricant composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 20. The method of claim 11, further comprising combining a minor amount of an engine oil additive composition with a major amount of the base oil mixture.
 21. A method for lubricating an engine component comprising: contacting said engine component with a lubricant composition wherein said lubricant composition has an ASTM Sequence IIIG Test kinematic viscosity increase of about 90% or less at 40° C. and average weighted piston deposits having about 5.5 or more merits, and wherein said lubricant composition comprises a major amount of a synergistic base oil mixture of a Group III base oil, a Group IV base oil, and a Group V base oil.
 22. The method of claim 21, wherein the Group III base oil is present in an amount of up to about 50 wt %, the Group IV base oil is present in an amount from about 20 wt % to about 45 wt %, and the Group V base oil is present in an amount from about 5 wt % to about 25 wt % based on the base oil mixture.
 23. The method of claim 21, wherein the lubricant composition is substantially free of a transition metal other than zinc.
 24. The method of claim 23, wherein the transition metal is selected from the group consisting of titanium and molybdenum.
 25. The method of claim 21, wherein the lubricant composition comprises at least about 250 ppm phosphorous.
 26. The method of claim 21, wherein the lubricant composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 27. The method of claim 21, wherein the lubricant composition provides improved oil consumption compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 28. The method of claim 21, wherein the lubricant composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group II base oil.
 29. The method of claim 21, wherein the lubricant composition provides improved viscosity increase control compared to a lubricant composition comprising a major amount of a base oil consisting of a Group III base oil.
 30. The method of claim 21, wherein the lubricant composition further comprises a minor amount of an additive composition. 